1. conjectural Apt implies a natural fitness or tendency; an impetuous person is apt to speak hastily. Liable refers to a contingency regarded as unfavorable; as, the ship was liable to founder at any momen Synonyms: likely, apt, conceivable, liable, probable, credible, conjectural, presumable, reasonable Antonyms: doubtful, improbable, questionable, unreasonable, dubious, incredible, unlikely